What's the main problem here?
Mid or Top feeding early?
Your team dominating early, but losing mid to late game inspite of it?
Not being able to secure objectives?
I lose so many matches because my team forces fights they can't win, then they flame for for not being there(as jungler).
Maybe try to play a carry role and make calls for your team.
It's a dice roll with most of these matches, but that is the best I can say.
As a support it's entirely up to everyone else. You may get your ADC ahead with good play, than the 5-0 Zed mid roams bot and kills you both.
I also got a lot of potato ADCs that can't farm or follow up on my engages, yet they flame me for being a bad support.
From my experience in low ELO, the only ADCs that solo carried match were Miss Fortune, Draven and Vayne.
Everyone else I am not too worried about as they can be stopped with a good team effort.
MF usually tends to decimate teams when given space, while Draven/Vayne straight kill everyone with lityle team help.